Of the many skin diseases of unknown etiology that affect man, the etiology of those diseases characterized by an accelerated rate of epidermal cell multiplication present one of the great challenges in epidermal cell biology and in experimental dermatology. One of these diseases, psoriasis, because of its prevalence and severity, remains one of the most perplexing of these diseases. Although some forms of topical therapy are effective in subduing the rapid proliferation of cells in this disease and its consequent scaling and disfigurement, there is no completely satisfactory method to treat this disease. Some systemic agents, such as methotrexate and hydroxyurea are presently in use, as well as the experimental procedure, PUVA (psoralen plus long ultraviolet light A) but their long-term use must be seriously questioned. This disease, and others, will continue to be an enigma until some appreciation of the ways epidermal cell regulation has evolved is known. We would therefore anticipate as new advances are made in the basic biology of cell growth and as new methods to control cell growth become known, a greater understanding of ways to approaching epidermal cell growth will be evident. One of the ways the transfer of this information can be accelerated is by a critical examination of ideas and hypotheses by scientists who have carefully thought about these problems for many years, who have written the definitive early studies, and who are the pioneers in experimental investigation. A symposium which is able to achieve this end will place in perspective the relevant information from the past 20 years and provide the direction and intellectual force for the next decade.